have been using this product for some time now. all of a sudden it wouldnt make any sound from any of the sources (radio, cassette, or ipod in the aux jack) all of the fuses are fine. when i press volume up or down i can hear the beep coming from the cars speakers. and i've made sure that i dont have it on mute as well as powering it off and powering it back on. cant figure out why it doesnt produce sound anymore.